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Continued radio observations of the persistent radio source associated with FRB20190520B provides insights into its origin

Arvind Balasubramanian, Mohit Bhardwaj, Shriharsh P. Tendulkar

TL;DR

This paper presents continued radio monitoring of the persistent radio source (PRS) associated with FRB20190520B, including the first low-frequency observations below $1$ GHz. The authors report a gradual decay in PRS brightness with episodes of brightening/dimming at 1.5 and 3 GHz, and identify a spectral break at $<1$ GHz attributed to absorption. Interpreting the data within the magnetar wind nebula (MWN) framework, they perform a joint spectro-temporal fit and obtain $t_{ m age}=52^{+16}_{-10}$ yr and $\alpha=1.77^{+0.07}_{-0.08}$. The results constrain the progenitor age and challenge the predictions of the hypernebula model, offering evidence for a young magnetar origin and implications for the PRS size via scintillation and emission mechanisms.

Abstract

Follow-up studies of persistent emission from fast radio burst (FRB) sources are critical for understanding their elusive emission mechanisms and the nature of their progenitors. This work presents new observations of the persistent radio source (PRS) associated with FRB 20190520B. We observe a gradual decay in the PRS brightness, which is punctuated by periods of brightening and dimming at both 1.5 and 3 GHz. Furthermore, our low-frequency ($<1$ GHz) observations--the first for this source--reveal evidence of a spectral break, which can be attributed to absorption processes. Interpreted within the framework of the magnetar wind nebula model, our data constrain the age of the magnetar progenitor to $52^{+16}_{-10}$ yr, broadly consistent with previous work. Assuming the observed 1.5 GHz variability is driven by scintillation, we discuss the constraints on the size of the persistent source. The observations presented here challenge the predictions of the previously published best-fit hypernebula model for this source.

Continued radio observations of the persistent radio source associated with FRB20190520B provides insights into its origin

TL;DR

This paper presents continued radio monitoring of the persistent radio source (PRS) associated with FRB20190520B, including the first low-frequency observations below GHz. The authors report a gradual decay in PRS brightness with episodes of brightening/dimming at 1.5 and 3 GHz, and identify a spectral break at GHz attributed to absorption. Interpreting the data within the magnetar wind nebula (MWN) framework, they perform a joint spectro-temporal fit and obtain yr and . The results constrain the progenitor age and challenge the predictions of the hypernebula model, offering evidence for a young magnetar origin and implications for the PRS size via scintillation and emission mechanisms.

Abstract

Follow-up studies of persistent emission from fast radio burst (FRB) sources are critical for understanding their elusive emission mechanisms and the nature of their progenitors. This work presents new observations of the persistent radio source (PRS) associated with FRB 20190520B. We observe a gradual decay in the PRS brightness, which is punctuated by periods of brightening and dimming at both 1.5 and 3 GHz. Furthermore, our low-frequency ( GHz) observations--the first for this source--reveal evidence of a spectral break, which can be attributed to absorption processes. Interpreted within the framework of the magnetar wind nebula model, our data constrain the age of the magnetar progenitor to yr, broadly consistent with previous work. Assuming the observed 1.5 GHz variability is driven by scintillation, we discuss the constraints on the size of the persistent source. The observations presented here challenge the predictions of the previously published best-fit hypernebula model for this source.

Paper Structure

This paper contains 7 sections, 3 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Observations
  3. uGMRT observations and archival data
  4. VLA observations and archival data
  5. Physical Interpretations
  6. Monotonic trend in the observations
  7. Magnetar Wind Nebula Model

Figures (3)

  • Figure 1: Light curve with all the flux density measurements from Table \ref{['tab:comprehensive_tab']} scaled to 1.5 GHz assuming a spectral index of -0.4. The fit is a linear regression showing a decreasing trend in the overall flux density over time.
  • Figure 2: Light curve of the FRB20190520B PRS, showing the joint spectro-temporal fit using Equation \ref{['eq:joint_fit']}. This fit gives an estimate of the age of the persistent source to be $t_{\rm{age}}=52$ years.
  • Figure 3: Spectrum of the PRS of FRB20190520B showing the joint spectro-temporal fit using Equation \ref{['eq:joint_fit']}. The color of the dashed lines represent the different epochs. The shaded blue region shows the uGMRT upper limits that suggest a break in the spectrum at frequencies $<1$ GHz.